Exemplary embodiments of the present invention relate to an integrated antenna device module for generating a terahertz continuous wave, and more particularly, to an integrated antenna device module for generating a terahertz continuous wave formed by directly depositing a photoconductor thin film on a silicon substrate and a fabrication method thereof.
A terahertz band (100 GHz to 10 THz) exists in an interface region between a light wave and a radio wave and is a frequency band technologically developed later. In order to develop the terahertz band, a new electromagnetic wave technology using the latest laser technology and semiconductor technology has been developed. The terahertz electromagnetic wave is oscillated in a pulse wave type using an ultra high speed photoconductive antenna (switch) based on a femtosecond optical pulse and a continuous wave type using an optical heterodyne scheme based on an optical mixer.
The terahertz band continuous wave system has been in the limelight as a terahertz spectroscopy or an imaging measurement system due to advantages such as frequency selectivity, price, size, measurement time, or the like, as compared with a pulse wave terahertz system.
When the continuous wave based on the optical heterodyne scheme inputs two continuous wave laser beams having the same strength but slightly different frequencies to the optical mixer formed on the photoconductive thin film such as low temperature grown (GaAs) of which carrier lifetime is short than picoseconds by aligning a wave surface, current modulation is generated in a terahertz band corresponding to a difference frequency and generated current is radiated as an electromagnetic wave in a terahertz band through an antenna.
Since a polycrystalline thin film can be grown regardless of a kind of a substrate, it is not necessarily to use a GaAs single crystal substrate so as to grow the existing LT-GaAs thin film. Therefore, the polycrystalline thin film can be grown even in silicon, quartz, sapphire, glass, or the like.
In particular, high-resistive silicon, which is a material having very high transmittance for the terahertz continuous wave, can be minimally absorbed into the existing GaAs substrate, thereby obtaining a stronger terahertz continuous wave signal.
Background art of the present invention is disclosed in KR Patent Laid-Open No. 10-2011-0061827 (Jun. 10, 2011).
In the related art, the LT-GaAs based photoconductive antenna device that has been widely in the photoconductive antenna is formed by depositing the photoconductor LT-GaAs thin film on the GaAs substrate, a photoconductive antenna electrode pattern on the LT-GaAs thin film, and then, attaching a substrate portion to a condenser lens made of the high-resistive silicon by cutting the photoconductor devices formed with each electrode pattern one by one.
However, the above-mentioned method needs to accurately align the electrode pattern with the center of the silicon lens and is very difficult to adhere the photoconductor device to the silicon lens so as to prevent a space from being formed between the substrate and the lens, when the photoconductor device is attached to the silicon lens.
In particular, when a slight space is present at the time of attaching the photoconductor device to the silicon lens, the scattering of the terahertz continuous wave is generated by an air layer, thereby causing the terahertz signal noise. Therefore, it is impossible to obtain the accurate spectroscopy or image.
Further, a semi-insulating GaAs substrate that is a semiconductor material has the lower transmittance for the terahertz continuous wave as compared with the high-resistive silicon, thereby reducing the terahertz signal to noise (SNR) ratio.